Construction of rotor for rotary mechanisms

ABSTRACT

The rotor comprises a plurality of rotor components produced by stamping and cutting sheet metal material and bonding the rotor components together into a unitary assembly. The regions of the assembly requiring surface hardening and machining are so treated.

United States Patent 1 1 1111 3,877,849

Wieland 1 1 Apr. 15, 1975 [54] CONSTRUCTION OF ROTOR FOR ROTARY1,701,392 2/1929 Short 29/1565 R MECHANISMS 1,854,455 4/1932 Day 29/1565R 2,341,836 2/1944 Wood 29/1565 R Inventor: Werner wielanmoberelseshelm,3,059,585 10/1962 Froede et a1 418/91 Germany 3,259,114 7/1966 Gassmann418/61 A ,299, 62 11967 P 41891 [731 Assignees: i NSU A1110 3,302,224211967 1213310161 418/91 s i fi g fi j 3,333,763 8/1967 Jungbluth et31.... 418/61 A an e -m- In 3,721,510 3/1973 Gilbert 418/13 Bodensee,both of Germany 3,740,175 6/1973 Kell 418/113 [22] Filed: Dec. 10, 1973[21] APPL NO: 423,159 Primary Examiner-John J. Vrablik Attorney, Agent,or FirmArthur Frederick [30] Foreign Application Priority Data Dec. 21,1972 Germany 2262619 [57] ABSTRACT 52 us. (:1 418/61 A; 418/91; 29/1565R The rotor comprises a plurality of rotor components [51] '3 CI Folc1/025 F04C 17/02; B2319 15/10 produced by stamping and cutting sheetmetal mate- [58] new of Search 418/6] 91; 29/1565 R; rial and bondingthe rotor components together into a 123/801 unitary assembly. Theregions of the assembly requir- [56] R f Ct d ing surface hardening andmachining are so treated.

e erences 1 e UNITED STATES PATENTS 1,282,936 10/1918 Pribil 29/1565 R13 Claims, 5 Drawing Figures CONSTRUCTION OF ROTOR FOR ROTARY MECHANISMSThe invention relates to rotors for rotary mechanisms of the Wankel elal. type disclosed in US. Pat. No. 2,988,065, and more particularly to alightweight rotor and the method of construction thereof.

BACKGROUND Heretofore, rotors for rotary mechanisms of the Wankel typehave been constructed of cast iron or aluminum and machine treated andworked to the desired finish and dimensions. The fabrication of theserotors require expensive molds and sand cores. The removal of allresidual sand from the hollow recesses of the castings is difficult andtime-consuming. In addition, the wall thicknesses of the cast rotor arerelatively great, necessitating relatively large bearing and shaftcomponents and an engine of relatively large weight to horsepower ratio.Further disadvantage of presently constructed rotors is that the wallsof the cast rotor are not uniform and therefore require accuratemachining to provide the finished rotor with the required dynamicbalance. The rotors which are produced by assembling machined and/orcast components, such as exemplified in the U.S. Pat. No. 3,059,585,suffer from some of the aforesaid disadvantages of the conventionalintegral, cast rotor.

It is therefore an object of this invention to provide a rotor forrotary mechanisms of the Wankel type, which rotor is of relativelysimple lightweight construction and wherein machine working andtreatment is minimal.

Another object of the present invention is to provide a rotor for arotary mechanism of the Wankel type, which rotor is capable of beingmore effectively cooled than heretofore known rotors.

A further object of this invention is to provide a rotor for a rotarymechanism of the Wankel type, the fabrication of which does not requireuse of casting molds or discs nor requires machine finishing of theouter surface, particularly the peripheral flank portions of the rotor.

A still further object of the present invention is to provide a methodof fabricating a rotor for a rotary mechanism of the Wankel type whichmethod includes the steps of securing together a plurality of rotorcomponents each of which is produced by stamping and cutting metal sheetmaterial.

A feature of this invention is the fabrication of component parts of therotor to desired size from flat sheet metal, such as steel, by a formingand cutting process, such as punch press operation, and then positioningand soldering or welding the components together into a lightweightassembly, having component wall thicknesses of uniform dimensions andrequiring no machine surface finishing or machining for dynamic balance.

SUMMARY Accordingly, the present invention contemplates a novel rotorfor a Wankel type rotary mechanism and method of fabrication thereofwhich rotor comprises a plurality of rotor components secured togetherinto an integral rotor assembly. More specifically, the rotor comprisesa two-piece hub secured together and connected on opposite sides to twoside wall members or elements, the side wall elements being secured attheir periphery to flank portions. The side wall elements are eachprovided with a hole coaxial with the bearing bore of the hub and of aslightly larger diameter than the hub bore. A tubular member extendsaxially and is connected at opposite ends to the side wall elements ateach of the apex portions of the latter members to provide, duringoperation, equalization of the pressure adjacent each of the side wallelements. The flank portions may be reinforced by brackets which areeach disposed between and secured to side wall elements, the hub and aflank portion. A solid bar is disposed at the adjacent ends of nextadjacent flank portions and between opposite side wall elements. Thesolid bars are secured at their opposite end portions to the end wallelements and to theend portions of the adjacent flank portions. Each ofthe solid bars are provided with an axially extending groove and openingfor accommodating an apex seal blade and pin assembly such as the typedisclosed in US. Pat. Nos. 3,400,691, 3,300,124 and 3,180,562. One ofthe side wall elements is provided with integrally formed internal gearteeth at the periphery of the hole therein. Each of the componentscomprising the rotor assembly is fabricated by stamping and cutting aflan, planchet or blank of sheet metal material, such as steel, whichcomponents are then secured together at their points of abutment bysoldering, brazing, or suitable bonding method, such as welding or epoxyadhesive gluing, to produce a unitary rotor assembly.

In accordance with the fabrication method of this invention thecomponents are formed and cut to the desired predetermined shape anddimensions. The solid bars are cut to the desired lengths from bar stockhaving the desired peripheral shape. The internal gear teeth in one ofthe side wall members is produced by accurate forming and cutting. It ispreferred that all of the components be first spot welded to one of theside walls so that gaps are left for solder. Thereafter, a pastelikesoldering material is applied to the gaps and the components at thepoint of abutment of the components to the other side wall element. Theother side wall element is then positioned in abutment on the othercomponents and the assembly is placed in a furnace to be heated andeffect a soldering of the components into a unitary assembly.Thereafter, the side wall element having the gear teeth-is subjected tohardening only in the region of the gear teeth in any suitable manner,such as by high frequency, induction heating and quenching. This is thenfollowed by the step of machine finishing the bearing hole of the hub,the internal gear teeth and forming the grooves and holes for receivingthe apex seal assemblies and side gas and oil seals.

In an alternative embodiment of the method of fabrication of the rotoraccording to this invention, the components may be secured together bysuitable welding techniques, such as electron-beam or laser-beam weldingtechniques and apparatuses.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will .be more fullyunderstood from the following detailed description thereof whenconsidered in connection with the accompanying drawing wherein oneembodiment of the invention is illustrated by way of example and inwhich:

FIG. 1 is a side elevational view of a rotor according to this inventionwith parts thereof broken away for illustration purposes;

FIG. 2 is an end elevational view of the rotor shown in FIG. 1;

FIG. 3 is a view in cross-section taken along line 33 of FIG. 1;

FIG. 4 is an exploded view of the components of the rotor shown in FIGS.1 to 3; and

FIG. 5 is a perspective view of two of the reinforcingbaffle platesforming part of the rotor assembly of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Now referring to the drawingsand more specifically FIGS. 1 to 4, the reference number generallydesignates a rotor according to this invention which rotor hasapplication to rotary mechanisms of the type disclosed in the US. Pat.No. to Wankel et al, 2,988,065. While the rotor 10 is shown as the typehaving three flank portions, the invention is not limited thereto. It istherefore to be understood that the invention has application to rotorshaving two or more than three flank portions without departure from thescope and spirit of the invention.

The rotor 10, as best illustrated in FIG. 4, comprises a plurality ofcomponents which are produced by stamping and cutting of flans,planchets or blanks of metal material, such as sheet-steel and thensecured together by suitable soldering, brazing, welding, epoxy gluing,or other bonding process- One of the rotor components is a bearing hub12 consisting of two identically shaped ring-shaped elements 14 and 16.Each ring-shaped element has a tubular body portion 18 and an integral,annular, radially extending flange portion 20. The ring-shaped elements14 and 16 are secured together in coaxial, mirror relationship at theirtubular body portions 18 so as to define a bearing hole 22.

Another rotor component is a side wall element 24 which has a body ofgenerally triangular shape with three intersecting arcuate-shaped edgesurfaces 26 which define apex portions 28. The side wall element 24 hasan outer surface 30 and an inner surface 32 and a cross-sectionaldimension greater than bearing hub 12 (see FIG. 2). A centrally locatedopening 34 is provided in the side wall element to extend through outersurface 30 and inner surface 32. The opening 34 is of a diameterslightly greater than the diameter of bearing hole 22 of bearing hub 12.

A second side wall element 36 constitutes another rotor component and isof the same triangular shape and size as side wall element 24. The sidewall element 36 has a cross-sectional dimension substantially the sameas side wall element 24 and have an outer surface 38 and an innersurface 40. The side wall element 36 is made from hardenable steelmaterial and is provided witha centrally located internal gear toothedportion 42 which is of substantially the same diametral size as opening34 in side wall element 24. Similar to side wall element 24, side wallelement 36 has three intersecting edge surfaces 44 which define apexportions 46.

Further components of rotor 10 are the three arcu ate-shaped flankelements 48 each of which has a depression 50 in the outer surfacethereof and a curvature complementary to the curvature of edge portions26 and 44 of side wall elements 24 and 36, respectively. The length ofeach flank element 48 is such that when assembled, the adjacent oppositeends thereof are in close spaced relation (see FIG. 1). The width ofeach flank element 48 is of such size that in the assembled condition,the flank element overlaps edge surfaces 26 and 44 (see FIG. 2).

As best shown in FIGS. 1, 2 and 3, rotor 10 also includes three pairs ofbrackets 52 which are disposed I adjacent each of the flank elements48and between bearing hub 16, side wall elements 24 and 36 and flankelements 48. As best illustrated in FIG. 5, each bracket 52 comprisestwo integral web portions 54 and 56 which lie in planes substantiallynormal to each other.

The web portion 54 has an edge surface 58 which has a configurationcomplementary to the shape of the inner surface of the adjacent flankelement 48 including part of depression 50, while web portion 56 has anedge surface 60 which is coextensive with edge surface 58 and has aconfiguration complementary to the shape of the inner surface of theadjacent flank element in another plane, including part of depression50. The web portion 54 also has an edge surface 62 curved to complementthe curvature of the outer peripheral surface of tubular body portion 18of bearing hub 12. The web portion 56 has an edge surface 64 that. inthe assembly,

extends axially in abutment against the outer peripheral surface of bodyportion 18. The web portion 56 also i' has an end edge surface 66 formedand dimensioned to abut the surfaces 32 and 40 of side wall elements 24and 36, respectively and the flanges 20 of bearing hub 12 (see FIG. 2).

The brackets 52 serve to structurally reinforce flank elements 48 and asbaffles for directing cooling fluid intothe spaces within the assembledrotonTo provide for directing the flow of lubricating oil employed as acoolant fluid, such as exemplified in the US. patents to Bentele et al.,No. 3,176,915, and Sollinger, No. 3,176,916, each pair of brackets 52(see FIG. 5) is disposed between the adjacent flank element 48, sidewall elements 24 and 36 and bearing hub 14 so that web portions 56 ofeach pair of brackets bisects one of three elongated inlet ports 68. Theinlet ports 68 are ar-r ranged in circumferential spaced relationship toeach other in one side of bearing hub 12. A plurality of elongatedoutlet ports 69 are arranged in circumferential spaced relationship toeach other in the opposite side of bearing hub 12 from inlet ports 68.In operation of rotor 10 the flow of cooling oil in ports 68 adjacentbrackets 52 is split as shown by the arrows in FIGS. 1,

2 and 3 by web portions 56 and each stream is guided by web portions 54radially outwardly toward the inner 1 surface of flank elements and thejuncture of the flank.

elements and the side wall elements 24 and 36 to which the flankelements are connected. The cooling oil also flows axially around theradially extending edges 55 of brackets 52 and thence out of outletports 69.

Improved cooling effectiveness is achieved according to this inventionat the juncture of flank elements 48 and side wall elements 24 and 36,by providing between inner surface 32 and edge surface 26 of side wallelement 24 a chamfered or beveled surface 70 and a similar beveledsurface 72 between inner surface 40 and edge surface 44 of side wallelement 36. The chamfered or beveled surfaces 70 and 72 expose more ofthe. inner surface of flank elements 48 to, the flow of cooling fluid sothat the flank elements are better cooled, particularly the flankelements of an internal combustion engine rotary mechanism, in which theflank elements are subjected to very high combustion gas temperatures.

While the present invention discloses brackets of the uniqueconfiguration shown in FIG. 5, the invention is not to be limitedthereto. The brackets can have any suitable shape to interconnect theflank elements and hub without departing from the scope and spirit ofthis invention.

Another component of rotor 12 is three solid metal bar inserts 74. Eachmetal insert is dimensioned in length to extend between the aligned apexportions 28 and 46 of end wall elements 24 and 36 and is receivable atits opposite ends in a notch 76 provided in the apex portions 28 and 46of end wall elements 24 and 36. The peripheral surface of the inserts ispolygonal in shape with two adjacent surfaces being formed complementaryto the inner surfaces of flank elements 48 so as to lie substantiallyflush against the flank elements. The metal inserts 74 serve to provideforthe machining of the grooves and bores for receiving apex sealassembly components, such as shown in Bentele US. Pat. Nos. 3,033,180and 3,180,562.

To insure during the operation of rotor 12 that the fluid pressureacting against side wall elements 24 and 36 is substantially equal, anopen ended tubular member 77 is secured at opposite ends in registeredholes 78 in each of the apex portions 28 and 46 of side wall elements 24and 36, respectively. The holes 78 are located radially inwardly of theside gas seals (not shown).

The method according to this invention of bonding the individualcomponents of rotor into a unitary structure is preferably accomplishedby soldering. it is preferred that all of the components of the rotor,except with respect to one of the side wall elements 24 or 36, are firstspot soldered to the other side wall element. For purposes of thisdescription it will be assumed that the parts are first attached to sidewall element 24. The interrupted points of soldering may be in closespaced relationship, as for example 0.2 mm or 0.3 mm apart. A solderingpaste of suitable composition, such as copper with an additive ofnickel, is applied where the parts contact between the soldered pointsand on the surfaces of contact between the rotor components and the sidewall element 36. The side wall element 36 is then placed in contactagainst the subassembly and the entire assembly is placed in a furnaceat a suitable temperature to effect melting of the solder. 1n the caseof a soldering paste of copper-nickel, a temperature of about 1100C(2282F) is preferred. After the rotor components are soldered together,side wall element 36, in the region of the internal gear tooth portion42, is surface hardened in any suitable manner, such as high frequencyinduction heating and quenching. Similarly, the surfaces 18 of bearinghub 12 defining the bearing hole 22 are also hardened. Thereafter, thetoothing of internal gear tooth portion 42 and the apex and side sealrecesses and grooves (not shown) are machined in any suitable mannerwell known to those skilled in machining practices.

In the alternative embodiment of the fabrication method, the rotorcomponents may be secured together by welding instead of soldering.Particularly suitable welding techniques are electron-beam andlaser-beam welding.

It is believed now readily apparent that the present invention providesa relatively lightweight balanced rotor. The invention also provides amethod of fabricating such rotor in which machining is minimal. Themethod provides the ability to accurately control rotor component wallthickness and shape so that dynamic imbalance is negligible.

Although several alternatives are revealed herein, it is to be expresslyunderstood that the invention is not limited thereto. Various changescan be made in the arrangement of parts and method steps withoutdeparting from the spirit and scope of the invention as the same willnow be understood by those skilled in the art.

What is claimed is: i

1. A rotor having a plurality of contiguous flank portions disposed foreccentric rotation within and relative to a housing cavity partiallydefined by a trochoidal peripheral surface, the rotor comprising:

a. a bearing hub having opposite end portions lying in planes normal tothe axis of the bearing hub;

b. two substantially congruent side wall elements disposed on oppositesides of said bearing hub and lying in substantially parallel planes;

c. a plurality of flank elements interconnecting the peripheral edgeportions of said two side wall elements and arranged in endwisealignment;

d. said bearing hub being dimensioned to extend between and engage saidside wall elements at the end portions;

e. each of the side wall elements having a plurality of inner peripheraledge surfaces each of which surfaces is provided with a chamfer adjacentan abutting flank element; and

f. said bearing hub, side wall elements and flank elements each beingconstructed of cut and formed sheet metal material and secured togetherinto a unitary structure.

2. A rotor having a plurality of contiguous flank portions disposed foreccentric rotation within and relative to a housing cavity partiallydefined by a trochoidal peripheral surface, the rotor comprising:

a. a bearing hub having opposite end portions lying in planes normal tothe axis of the bearing hub;

b. two substantially congruent side wall elements disposed on oppositesides of said bearing hub and lying in substantially parallel planes;

c. a plurality of flank elements interconnecting the peripheral edgeportions of said two side wall elements and arranged in endwisealignment;

d. said bearing hub being dimensioned to extend between and engage saidside wall elements at the end portions;

c. said bearing hub having an open ended tubular portion and radiallyextending, annular flange portions integral with and at the oppositeends of the tubular portion;

f. the bearing hub having a plurality of circumferentially spacedopenings therein which serve in the use of the assembled rotor to passcooling fluid into the space between the annular flange portions;

g. a plate disposed between the side wall elements,

the tubular and annular flange portions of the bearing hub and adjacenteach of said openings for dividing the cooling fluid stream in twostreams and deflecting each of the two streams in opposite directionscircumferentially of and radially outward from the bearing hub; and

h. said bearing hub, side wall elements, flank elements and the platebeing constructed of cut and formed sheet metal material and securedtogether into a unitary structure.

3. A rotor having a plurality of contiguous flank portions disposed foreccentric rotation within and relative to a housing cavity partiallydefined by a trochoidal peripheral surface, the rotor comprising:

a. a bearing hub having opposite end portions lying in planes normal tothe axis of the bearing hub;

b. two substantially congruent side wall elements disposed on'oppositesides of said bearing hub and lying in substantially parallel planes;

c. a plurality of flank elements interconnecting the peripheral edgeportions of said two side wall elements and arranged in endwisealignment;

d. said bearing hub being dimensioned to extend between and engage saidside wall elements at the end portions;

e. each side wall element has a plurality of peripheral edge surfaceswhich converge to define a plurality of apex portions;

f. a solid bar for each pair of apex portions disposed to extend betweenthe apex portion of one side wall element to the corresponding apexportion of the other side wall element to thereby interconnect the sidewall elements and to provide material in which recesses can be providedfor receiving apex seal devices; and said bearing hub, side wallelements and flank elements each being constructed of cut and formedsheet metal material and secured together and to said solid bars into aunitary structure.

4. The apparatus of claim 3 in which'an opening is provided in each apexportion of each of said side wall elements to receive the solid barstherein.

5. The method of fabricating a rotor having two spaced side wallelements interconnected at their periphery by a plurality of contiguousconverging flank portions, the rotor being for use in a rotary mechanismof the type having a rotor cavity partially defined by a trochoidalperipheralsurface, the method comprising the steps of:

a. forming by stamping and cutting a bearing hub from relatively thinsheet metal material;

b. forming by stamping and cutting two substantially congruent side wallelements having a plurality of converging edge surfaces from relativelythin sheet metal material;

c. forming by stamping and cutting a plurality of flank elementscorresponding in number to the number of edge surfaces of each of theside wall elements; (1. cutting solid metal inserts from bar stock tothe length required for each insert to extend between the side wallelements at each of the points of con-.

vergence of the flank elements; and

e. assembling and bonding the bearing hub, inserts, flank elements andsaid side wall elements into a unitary structure. i

6. The method of claim 5 wherein bonding is accomplished by soldering.

7. The method of claim 5 wherein bonding is accomplished by welding.

8. The method of claim 5 wherein bonding comprises applying a paste-likesoldering mediumto the areas of contact between the bearing hub, sidewall elements, inserts and flank elements and exposing the entire assembly to sufficiently high temperatures to melt the soldering medium.

9. The method of claim 8 wherein the soldering medium is a copper solderwith anickel additive and the assembly is exposed to a temperature ofabout 1100C.

10. The method of claim 5 wherein assembling and bonding comprises thestep of:

a. assembling the bearing hub, inserts, flank elements in properrelationship to each other and one of the side wall elements, andsoldering these components together at spaced points in the region ofcontact;

b. applying solder to the spaces between the points of solder, and onthe regions of contact with the other side wall elements;

0. positioning said other side wall element into the assembly; and,

d. heating the entire assembly to melt the solder to render the assemblya single unitary structure.

11. The method of claim 10 wherein the points of solder are spaced apartbetween about 0.2 mm and about 0.3 mm.

12. The method of claim 5 wherein one of said side wall elements isformed to have internal gear teeth and, I after assembly and bonding,the region of the internal gear teeth is hardened.

13. The method of claim 12 wherein hardening is by the process of highfrequency induction heating and quenching.

1. A rotor having a plurality of contiguous flank portions disposed foreccentric rotation within and relative to a housing cavity partiallydefined by a trochoidal peripheral surface, the rotor comprising: a. abearing hub having opposite end portions lying in planes normal to theaxis of the bearing hub; b. two substantially congruent side wallelements disposed on opposite sides of said bearing hub and lying insubstantially parallel planes; c. a plurality of flank elementsinterconnecting the peripheral edge portions of said two side wallelements and arranged in endwise alignment; d. said bearing hub beingdimensioned to extend between and engage said side wall elements at theend portions; e. each of the side wall elements having a plurality ofinner peripheral edge surfaces each of which surfaces is provided with achamfer adjacent an abutting flank element; and f. said bearing hub,side wall elements and flank elements each being constructed of cut andformed sheet metal material and secured together into a unitarystructure.
 2. A rotor having a plurality of contiguous flank portionsdisposed for eccentric rotation within and relative to a housing cavitypartially defined by a trochoidal peripheral surface, the rotorcomprising: a. a bearing hub having opposite end portions lying inplanes normal to the axis of the bearing hub; b. two substantiallycongruent side wall elements disposed on oppositE sides of said bearinghub and lying in substantially parallel planes; c. a plurality of flankelements interconnecting the peripheral edge portions of said two sidewall elements and arranged in endwise alignment; d. said bearing hubbeing dimensioned to extend between and engage said side wall elementsat the end portions; e. said bearing hub having an open ended tubularportion and radially extending, annular flange portions integral withand at the opposite ends of the tubular portion; f. the bearing hubhaving a plurality of circumferentially spaced openings therein whichserve in the use of the assembled rotor to pass cooling fluid into thespace between the annular flange portions; g. a plate disposed betweenthe side wall elements, the tubular and annular flange portions of thebearing hub and adjacent each of said openings for dividing the coolingfluid stream in two streams and deflecting each of the two streams inopposite directions circumferentially of and radially outward from thebearing hub; and h. said bearing hub, side wall elements, flank elementsand the plate being constructed of cut and formed sheet metal materialand secured together into a unitary structure.
 3. A rotor having aplurality of contiguous flank portions disposed for eccentric rotationwithin and relative to a housing cavity partially defined by atrochoidal peripheral surface, the rotor comprising: a. a bearing hubhaving opposite end portions lying in planes normal to the axis of thebearing hub; b. two substantially congruent side wall elements disposedon opposite sides of said bearing hub and lying in substantiallyparallel planes; c. a plurality of flank elements interconnecting theperipheral edge portions of said two side wall elements and arranged inendwise alignment; d. said bearing hub being dimensioned to extendbetween and engage said side wall elements at the end portions; e. eachside wall element has a plurality of peripheral edge surfaces whichconverge to define a plurality of apex portions; f. a solid bar for eachpair of apex portions disposed to extend between the apex portion of oneside wall element to the corresponding apex portion of the other sidewall element to thereby interconnect the side wall elements and toprovide material in which recesses can be provided for receiving apexseal devices; and g. said bearing hub, side wall elements and flankelements each being constructed of cut and formed sheet metal materialand secured together and to said solid bars into a unitary structure. 4.The apparatus of claim 3 in which an opening is provided in each apexportion of each of said side wall elements to receive the solid barstherein.
 5. The method of fabricating a rotor having two spaced sidewall elements interconnected at their periphery by a plurality ofcontiguous converging flank portions, the rotor being for use in arotary mechanism of the type having a rotor cavity partially defined bya trochoidal peripheral surface, the method comprising the steps of: a.forming by stamping and cutting a bearing hub from relatively thin sheetmetal material; b. forming by stamping and cutting two substantiallycongruent side wall elements having a plurality of converging edgesurfaces from relatively thin sheet metal material; c. forming bystamping and cutting a plurality of flank elements corresponding innumber to the number of edge surfaces of each of the side wall elements;d. cutting solid metal inserts from bar stock to the length required foreach insert to extend between the side wall elements at each of thepoints of convergence of the flank elements; and e. assembling andbonding the bearing hub, inserts, flank elements and said side wallelements into a unitary structure.
 6. The method of claim 5 whereinbonding is accomplished by soldering.
 7. The method of claim 5 whereinbonding is accomplished by welding.
 8. The method of claim 5 whEreinbonding comprises applying a paste-like soldering medium to the areas ofcontact between the bearing hub, side wall elements, inserts and flankelements and exposing the entire assembly to sufficiently hightemperatures to melt the soldering medium.
 9. The method of claim 8wherein the soldering medium is a copper solder with a nickel additiveand the assembly is exposed to a temperature of about 1100*C.
 10. Themethod of claim 5 wherein assembling and bonding comprises the step of:a. assembling the bearing hub, inserts, flank elements in properrelationship to each other and one of the side wall elements, andsoldering these components together at spaced points in the region ofcontact; b. applying solder to the spaces between the points of solder,and on the regions of contact with the other side wall elements; c.positioning said other side wall element into the assembly; and, d.heating the entire assembly to melt the solder to render the assembly asingle unitary structure.
 11. The method of claim 10 wherein the pointsof solder are spaced apart between about 0.2 mm and about 0.3 mm. 12.The method of claim 5 wherein one of said side wall elements is formedto have internal gear teeth and, after assembly and bonding, the regionof the internal gear teeth is hardened.
 13. The method of claim 12wherein hardening is by the process of high frequency induction heatingand quenching.